Electrical kinda people step in

turtleman

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Sep 6, 2009
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I've come up with a little project to hopefully improve upon my nitrous system. I have an idea that I feel aught to be doable but there's a few things I'm not familiar enough with. I'm gonna try to be as concise as I can.

I'm using a Harris Speed Works "the interface" controller to give me the fueling for nitrous through the maf signal. It works brilliantly but it's lacking one feature that I'd like to try to integrate and that is compensation for bottle pressure since it decreases during a run and makes me progressively richer and thus slower as I go down the strip.

One feature of this controller (that I do not use or ever intend to use for it's intended purpose is the rpm-based enrichment function which taps into your rpm lead and richens the result maf adjustment up to a preset amount. The manual for the controller says it will adjust up to 8000rpm and can be set as high as 15%. Based off my rough calculations, 15% is enough to give me bottle pressure fueling compensation for a range of about 150psi which would help with the degrading pressure issue while I'm spraying. More would be nice but that's enough for the trouble I think.

So the controller is looking for an rpm signal - I want to take a standard 0-5v nitrous pressure sender and digitally translate that into a made-up rpm signal. I'm figuring I'd need some kind of programmable micro-controller/programmable IC type deal to input the voltage and give me an rpm signal and then tune the ranges such that it works for my nitrous controller. I don't know exactly what my controller does as far as the relation between rpm and the preset fuel adjustment percentage but I could test and figure that out by plotting its output vs rpm after I have a way to do that.

So where I'm left with some questions is does anyone know exactly what the rpm lead for my nitrous controller is looking for from an electrical standpoint? In other words, I don't really know what an rpm or tach signal is in this case (it's meant for an LS1,LS2,etc btw). Secondly, I'm not as much of a geek as I wish I was - what can I use to do this whole digital I/O conversion?

If anyone has any other totally different ideas about how I could accomplish this blast away!



This is what rpm signal sources the controller uses by the way
HSWtachwire.png
 

rocket5979

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Nov 15, 2005
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Round Lake, IL
I have an idea. NANO!

You way sounds too complex and cumbersome, and at the end of the day, you still have nitrous pressure drop. With a NANO it cures the root issue so there is no need to do any electronics modifications or fangling. Another item worth mentioning is that unless you are spraying a really large shot your bottle pressure isn't exactly going to drop like a stone after one run down the track. What size shot are you spraying?
 

turtleman

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This is the first I've ever heard of NANO honestly. Thanks - I'm gonna search & read now..

I'm not spraying a big shot but I can see I'm loosing a fair amount of bottle pressure in a run. I can't remember exactly what it was falling to last I was at the track but it was enough to throw fueling off more than I like and I plan to spray more and longer than I was. I want to spray 100-125 from my single point behind the throttle body if I can. At the track last year, I was doing a 75 shot and was loosing a few hundred psi I wanna say - 1100 at the start and like 800 at the end - it's hard to say because I got no clean nitrous runs in due to running out of maf - obviously fixed that issue now

Thanks again for the suggestion there. If that will maintain pressure reliably, then that eliminates the problem altogether - not gonna argue with that!
 

turtleman

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When I started tuning nitrous, I was going for 950psi bottle pressure but I found on some hot summer days (like say 90-95F), it'll get up to 1100psi without the heater so I figured I'd not fight mother nature and work with that. I can make the bottle hotter - can't make it cooler. Although yeah it looks like it's general consensus that you get more pressure taper if you start out with higher pressure. I guess I'll just tune it for 950 and uh.. never spray on a hot day I guess :dunno:
 

OffshoreDrilling

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all of this is way overkill. Continue using your current setup and save yourself the hundreds, if not a thousand dollars. If you want to "improve" your nitrous system, put a bigger jet in the nitrous line.

On my previous truck i was spraying 150 dry with that controller as well. Zero problems.
 

wolfe

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Jun 2, 2008
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This is the first I've ever heard of NANO honestly. Thanks - I'm gonna search & read now..

I'm not spraying a big shot but I can see I'm loosing a fair amount of bottle pressure in a run. I can't remember exactly what it was falling to last I was at the track but it was enough to throw fueling off more than I like and I plan to spray more and longer than I was. I want to spray 100-125 from my single point behind the throttle body if I can. At the track last year, I was doing a 75 shot and was loosing a few hundred psi I wanna say - 1100 at the start and like 800 at the end - it's hard to say because I got no clean nitrous runs in due to running out of maf - obviously fixed that issue now

Thanks again for the suggestion there. If that will maintain pressure reliably, then that eliminates the problem altogether - not gonna argue with that!

GM high tech did a write up on it a few years ago. I'll see if I can find a link or the article and throw it up in here. There was quite a difference on the dyno when they used it and when they didn't.
 

rocket5979

Gearhead
Nov 15, 2005
6,576
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Round Lake, IL
Your bottle pressure is too high to begin with. Run it around 900-950psi and tune accordingly...You'll see less of an overall pressure drop and get more consistent times.

Yep, at a given rough percentage of pressure drop, if you start lower in pressure then you will end up numerically closer to that starting point in the end of things.

When I started tuning nitrous, I was going for 950psi bottle pressure but I found on some hot summer days (like say 90-95F), it'll get up to 1100psi without the heater so I figured I'd not fight mother nature and work with that. I can make the bottle hotter - can't make it cooler. Although yeah it looks like it's general consensus that you get more pressure taper if you start out with higher pressure. I guess I'll just tune it for 950 and uh.. never spray on a hot day I guess :dunno:

I guess what route you end up taking depends on whether you intend to use your system at the track only. In that case then taking the bottle out and keeping it cool isn't a big deal to keep pressure lower; or as someone else mentioned, just purging the pressure down. For a race, usually the results warrant the wasting of a bit of nitrous needed to purge down. However, if it is meant for street fun then obviously it would be an expensive pita to do that all the time, so I can see you just dealing with the higher pressure if it comes to that.

Buy ice and/or purge it down to the right pressure. Maintaining correct bottle pressure is part of tuning/racing. Also, running high pressures can lead to issues with the nitrous solenoid being held shut, etc.

Many nitrous solenoids are rated for higher than 1100psi. I don't consider it being "too high" until it starts to close in on middle 1100's, then it's too friggin high. It really depends on which solenoids you have and how hard of a hit you want off the launch. However, I agree that most street and weekend racer systems benefit from lower bottle pressure because they usually aren't running monster solenoids to handle the higher pressure with nitrogen push systems to keep pressure loss at a minimum. Setting solenoid plunger height (if adjustable) can also cure pressure lockup issues when running nitrous at high pressure.
 

Turbocharged400sbc

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cheapest solution would be to increase volume, bigger bottle or two big bottles.

getting a circuit setup to convert a 0-5v analog pressure signal into an adjustable "AFC" of sorts would be a pain....

using that signal to vary a 0-5v ECT or IAT sensor signal would be far easier and less likely to result in a major fuckup than a custom experimental box doing frequency modification via an analog signal....

both sensors have tables that can be utilized for a track only tune...
 

deviantlx

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Apr 20, 2008
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cheapest solution would be to increase volume, bigger bottle or two big bottles.

getting a circuit setup to convert a 0-5v analog pressure signal into an adjustable "AFC" of sorts would be a pain....

using that signal to vary a 0-5v ECT or IAT sensor signal would be far easier and less likely to result in a major fuckup than a custom experimental box doing frequency modification via an analog signal....

both sensors have tables that can be utilized for a track only tune...


correction. cheapest solution is to run the right bottle pressure. then he will see almost no drop. :io:
 
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